A substrate processing system including a single substrate processing apparatus is known. The single substrate processing apparatus rotatably holds a substrate around a vertical axis and rotates the substrate to supply various processing liquids to a target surface of the substrate from a nozzle. In order to normally actuate the substrate processing system, a user needs to check that the nozzle of each substrate processing apparatus appropriately ejects the processing liquids. In Japanese Patent Laid-Open Publication No. 2003-136015, a CCD camera that photographs the processing liquid ejected from the nozzle and a container that receives the ejected processing liquid are installed in a processing chamber of the substrate processing apparatus to check an ejection state of the processing liquid from a photographed image of the CCD camera.